[ARM] clps711x: fix warning in edb7211-mm.c

Fix:
include/asm-generic/pgtable.h:305: warning: 'struct vm_area_struct' declared inside parameter list
include/asm-generic/pgtable.h:305: warning: its scope is only this definition or declaration, which is probably not what you want
include/asm-generic/pgtable.h:317: warning: 'struct vm_area_struct' declared inside parameter list
include/asm-generic/pgtable.h:331: warning: 'struct vm_area_struct' declared inside parameter list

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>